Piezo-electric device



April 28, 1931.

C. B. SAWYER PIEZO-ELECTRIC DEVICE Original Filed May a, 1927 F1 Ha I INVENTOR ATTORNEYS Patented Apr. 28, 1931 I STAES CHARLES B. SAWYER, F CLEVELAND HEIGHTS, OHIO, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE CLEVELAND TRUST COMPANY, OF CLEVELAND, OHIO, A CORPORA- .TION OF OHIO Application filed May 6, 1927, Serial No.

This invention relates to piezo-electric material and more particularly to an lmproved method and means for utilizing the piezoelectric efl'ect of such material.

In piezo-electric devices for use at: audlo frequencies various piezo-electric materials such as quartz and the like have been employed. In general, however, the quartz has not been found sensitive enough for such work so that Rochelle salt crystals have been used for this purpose, due to the greater piezo-electric effect obtained therefrom. The

Rochelle salt crystals usually employed for such purposes, however, have had certain disadvantages, such as inconstancy of the piezoelectric efiect produced, non-permanency of the crystals, etc.

An object of this invention is to provide piezo-electric elements of rugged character.

A further object of the invention is to provide piezoelectric elements of uniform character giving uniform piezo-electric results.

Another object of the invention is to provide piezo-electrie elements of relatively 2 great sensitivity or relatively great piezoelectric eifect.

A further object of my invention is to provide piezo-electric elements whereby the motion of the elements due to an electrostatic field may be magnified to give a correspondingly greater mechanical efieet.

Another object of this invention is to provide a iezo-electric element of advantageous piezo-e ectric characteristics capable of being produced by economical use of piezoelectric material.

A further object of the invention is to provide a piezo-electric element suitably constrained whereby when the element is subjected to an electrostatic field the element may be given a bending motion to provide a magnified mechanical motion thereof.

Another object of my'invention is to 'pro vide an improved method 'for utilizing the piezo-electric effect of piezo-electric material.

A further object of this invention is to provide piezo-electric devices whereby improved piezo-electric effects may be obtained.

Other objects of my invention will be ap- PIEZO-ELECTRIC DEVICE ensues 189,443. Renewed November 18, 1930.

parent to those skilled inthe art from the following description and annexed drawings.

My invention contemplates generally the provision of piezo-electric elements of permanent and sensitive characteristics, said elements embodying piezo-electric material suitably constrained whereby a magnified mechanical motion of said element may be obtained when subjected to an electrostatic field. More specifically, my invention contemplates a piezo-electric element embodying a piezo-eleciric material arranged to elongate or contract when subjected to a given electrostatic field, the said material being suitably constrained whereby under said given electrostatic field a bending motion may be produced to obtain a magnified mechani-' cal motion of the element.

In the drawings:

Figure 1 is a perspective view of a Rochelle salt crystal from which the piezo-electric material for my invention may be obtained.

Fig. 2 is a perspective view of a slab of piezo-electric material such as Rochelle salt, portions thereof for my improved device being indicated in dotted lines.

Fig. 3 is an end elevation of a piezo-electric element of my invention, said element being Fig. 5 is a front elevation of the structure shown in Fig. 4.

Fig. 6 is an end elevation of another modified form of element contemplated .by my invention mounted on a suitable support.

Fig. 7 is an end elevation of the structure shown in Fig. 6 showing in exaggerated-form the motion of the element when subjected to an electrostatic field.

Fig. 8 is a front elevation of a piezoelectric device contemplated by my invention embodying a modified form of element, said device embodying a jewel for cutting phonograph records; and

Fig. 9 is an end elevation of the structure shown in Fig. 8, a conical acoustic diaphragm being shown associated with the element.

While various piezo-electric materials may be employed in constructing an element acrding to my inventipn, I prefer to employ erefor portions obtained from Rochelle salt ystals. Thus, the material for an element my invention may be obtained from a ochelle salt crystal 1 as illustrated in Fig. 1, c said crystal having the major longitudi- Ll axis c--0, the major transverse axis 12-?) 1d the minor axis a-a. As an illustration F one manner in which my improved element ay be constructed, I may cut or otherwise )tain from a crystal 1 or portion thereof a ab 2 illustrated in Fig. 2, said slab being referably cut so that its parallel faces 3 are ibstantially parallel to the major crystalline xes and substantially perpendicular to the llIlOI' crystalline axis. It will be under :ood, however, that a slab such as 2 might be btained from other piezo-electric materials. At 4 and 5 in dotted lines in Fig. 2 I have .lustrated how portions to be used in my nproved element may be obtained from the lab 2. At 4 is shown a portion of trapezoidal hape whereas at 5 is shown a portion of subtantially rectangular shape. The portions 4 nd 5 are preferably so cut from the slab 2 hat the longitudinal axes M--M and N-N .re at substantially 45 degrees to the major rystalline axes, for reasons to be further disussed hereinafter. The faces of the portions and 5 are substantially parallel. It will be inderstood, of course, that the portions 4 and i may be out directly from a crystal such as 1, r a portion thereof.

In Fig. 3, the crystal portion 6 is shown iecured at one end thereof to a suitable support 7 such as of lead by adhesive material 8 110l1 as, for example, shellac or Canada )alsam. The faces 9 and 10 of the portion 6 nay be of rectangular or trapezoidal shape as illustrated in Fig. 2 or of any other suitable ;hape. To the face 10 is shown secured a suitable electrode 11 such as of tin foil, Which electrode preferably contacts with a relatively large portion of the face 10. The wire 12 is connected to the electrode 11. To the o posed face 9 is shown secured a portion 13 w ich may be of metal, such as aluminum, and may be relatively thin but of suificient strength to constrain the crystal portion 6. The crystal portion 6 and metal portion 13 constitute what may be termed the piezoelectric element 14. The portion 13 preferably, though not necessarily, is co-extensive with the face 9 of the portion 6 and is preferably secured to said portion throughout said face 9 as b suitable adhesive material, the portion 13 eing secured to the support 7 as by the" adhesive material 8. A wire 15 is secured to said metallic portion-whereby the portion 13 may act as an electrode. If the crystal portion 6 is cut from aficrystaljin'the manner indicated in Fig.2, thef slaidportion 6' when subjected to an electrostatic-field by the .electrodes 11 and 13 willtendtocontract or elongate, depending upon the direction of 1 is applie said field. Since, however, the motion of said portion 6 is constrained by the portion 13, the crystal portion 6 is not free to elongate or contract, but actually undergoes a bending motion, whereby the upper edge 16 of the crystal portion 6 actuall chanical motion than if t e crystal portion 6 were unconstrained by the portion 13.

In Figs-'4 and 5 I have shown a modified form of my invention wherein the crystal portions 17 and 18 are shown in juxtaposed position, the said portions being both secured to a support 19 by adhesive material 20. The faces 21, 22, 23 and 24 of the crystal portions 17 and 18 may be of rectangular shape, as shown in Fig. 5, or of any suitable shape such as discussed in connection with Fig. 3. The adjacent faces 22 and 23 may be secured to each other throughout their extent by suitable cement whereby the crystal portion 17 acts to constrain the motion of the crystal portion 18, and vice versa. Electrodes 25 and 26 are shown as associated with the faces 21 and 24 and wires 27 and 28 and secured respectively to said electrodes. The crystal portions 17 and 18 are so oriented that under a given electrostatic field-one of said crystal portions tends to contract and the other crystal portion tends to elongate longitudinally. Under such conditions, when the piezo-electric element 29 comprising the crystal portions 17 and 18, is subjected to an electrostatic field by means of the electrodes 25 and 26, a greater bending motion of the top edges 30 and 31 is obtained, due to the simultaneous contraction of the portion 17 and elongation of the portion 18, and vice versa.

has a greater me- In Figs. 6 and 7 are shown another lnodified form of piezo-electric element comprising the crystal portions 32 and 33 having the adjacent edges 34 and 35, said portions being secured to the support 36 by suitable adhe; s1ve material 37. To the outer faces 38 and 39 are shown secured electrodes 40 and 41 respectively connected by the Wires 42 and 43 to a single wire 44, said electrodes 40 and 41 thereby forming a single terminal. Intermediate the inner faces 34 and 35 is shown a relatively thin electrode 45 which preferabl is coextensive with the faces 34. and 35. Siich electrode may be constituted of aluminum foil. To said electrode is secured a wire 46. The electrode 45 thus forms one terminal and the electrodes 40 and 41 the other terminal. The crystal'por'tions 32 and 33 are preferably so oriented that under a given electrostatic field both portions tend .to expand or contract longitudinally. When a given voltage "to the wires 46 and 44 it will be readily seenrthat the crystal portions 32 and 33 are; subjected to electrostatic fields in opposite directions, whereby under said given I voltage the portion 32 will tendto contract i 'are'rigidly attachedto the, brackets 12 and the force being exerted by the stressedmemthe pins 27 have revolubly mounted upon them rollers 37 which in this modification serveas the stops to. limit the deflection of the member 8. The ends of theclamps 16? are in the form of pins upon which rollers 18, are revolubly mounted so as to facilitate movement of the member 8 therepa st. Similarly the pin 28' carried by the rod 6 has mounted upon it a roller 7 adapted to bear against the member 8 intermediate the two rollers 37 and slightly displaced therefrom. Another advantage of this modification in addition to compensating for slippage of the member 8' past the deflecting means, is that it may in this formbe used upon a stressed member 8' which is moving in relation to the measuring device, such as a belt or the like, and thus used as a dynamometer to measure ber.

to by an ad usting screw 42 having its inner end in engagement with the plate 41 and threaded through a bracket 43 rigid with the chamber 1. This movable plate pro- .vides convenient means for compensating for variations in pressure of the fluid 31 resulting from variations in temperature, and

which would otherwise tend to produce inaccuracies in the reading of the indicating and recording instruments.

The operation of my device is substantially as follows: v

- The indicating gauge 32 should first be i observed to determine whether or not the hand points directly to the zero 'mark when 'duced; and if the member 8'is under tension -a side thrust will be produced against a rod the instrument is not positioned upon the stressed "member. If this is not the case the proper adjustment may be obtained by manipulating a screw 42 to increase or decreasethe pressure of. a fluid 31, as the requirements of the case shall dictate. Then the device is positioned 'upon the stressed member 8, as previously described, and the screws 7 22 tightened until the ends 18 of the clamps l6 pull the member 8into contact with the ends 37 of the arms 13, or the rollers 37 depending upon which modification of the device is being employed. Owing to the displacement of the' end 7 of the rod 6 from a line joining the'ends 37 of the arms 13 a-deflection inthe member 8 will thus be pro- 6 to compress the receptacle 3 and its contamed fluid, increasing the pressure thereof.

This pressure will be communicated to-and indicated the pressure gauge 32 or to a recording instrument in the event that such isthe type of instrument being employed, or

both. The relation between the indicated orthe recorded pressure, as the case maybe,

of said fluid.

posed upon a member, comprising a chamber, a piston reciprocal within said chamber,a receptacle of flexible material disposed within and conforming to said chamber and piston, a'rod carried by said piston and extending from the chamber to engage said stressed member, means for deflecting said stressed member towards said chamber on 0pposite sides of said rod, a fluid in said receptacle, and means for mea'suring the pressure 29A device for measuring the stress im posed upon a member, comprising a chamber, a piston reciprocal within said chamber, a receptacle of flexible material disposed within and conformin to saidchamber andlpi'stou, a. rod carried y said piston and extending A portion of one wall of the chamber 1 is (from the chamber to g Said stressed formed'by a plate 41 movable in respect there 3. A 'device for'measuring' the stress imposed upon a member, comprising a chamber, a piston reciprocal within said cham-.

.ber, a receptacle of flexible material disposed within and conforming to said chamber and piston, a rod carried by said pistonand extending from the chamber to engage" said stressed member, means for deflecting'sa1d.

stressed member towards said chamber on opposite sides of said rod, a.flu1d 1n sald receptacle, means for measuring thepressure oflsaid fluid, and means for permitting longitudinal movement of said stressed member in respect to said measuring device while de- 4. A device for measuring the stress im-' posed upon a. member, comprising a chamber, a compressible receptacle in said chamber, a piston reciprocal within said-chamber and adapted to compress said comp ressible receptacle, a rod carried by said piston and extending from'the chamber to engage said stressed member, means for deflecting said stressed member towards said chamber on opposite sides of'said rod, a fluid in said receptacle,iand means for measuring the pressureof said fluid.

5. A device .for measuring the stress immember towards said chamber on opposite sides of said rod, a fluid in said receptacle, means for measuring the pressure of said fluid, and means for compensating for pressure changes of said fluid.

6 A device for measuring the stress imposed upon a member, comprising a chamber, a compressible receptacle within said chamber, a piston reciprocal Within said chamber and adapted to compress-said compressible receptacle, a rod carried by said piston and extending from the chamber to engage one side of said stressed member, a pair of brackets extending from said chamber on opposite I sides thereof, a clamp pivoted to each of said brackets and adapted to engage the other side of said stressed member, means for tightening said clamps to deflect said member towards said chamber on opposite sides of said rod, a fluid in said receptacle, and means for measuring the pressure of said fluid.

7. A device for measuring the stress imposed upon a member, comprising a chamber, a compressible receptacle within said cham her, a piston reciprocal Within said chamber and adapted to compress said compressible receptacle, a rod carried by said piston and extending from the chamber to engage one side of said stressed member, ets extending from said chamber on opposite sides thereof, a clamp pivoted to each of said brackets and adapted to engage the other side of said stressed member, means for tightening said clamps to deflect said member towards said chamber on opposite sides of said rod, a fluid in said receptacle, means for measuring the pressure of said fluid, and means for compensating for pressure changes of said fluid.

8. A device for measuring the: stress im-,

posed upon a member, comprising a chamber, a compressible receptacle within said chamher, a piston reciprocal within said chamber and adapted to compress said compressible receptacle, a rod carried by said piston and extending from the chamber to engage one side of said stressed member, a pair of brackets extending from said chamber on opposite sides thereof, a clamp pivoted to each of said brackets, a roller revolubly mounted on each of said clamps and engaging the other side of said stressed member, means for tightening said clamps to deflect said member to- Wards said chamber on opposite rod, a fluid in said receptacle, and means for measuring'the pressure of said fluid.

9. A device for measuring the stress imposed upon a member, comprlsing a chamber, a compressible receptacle Within said chamher, a piston reciprocal within said chamber and adapted to compress said compressible receptacle, a rod carried by said pistonand extending from the chamber to engage one side of said stressed member, a pair of brackets extending from said chamber on opposite sides thereof, a clamp pivoted to each of said a pair of bracksides of the brackets, a roller revolubly mounted on each of said clamps and engaging the other side ofs'aid stressed member, means for tightening said clamps to deflect said member towards said chamber on opposite sides of the rod, a fluid in said receptacle, means for measuring the pressure of said fluid, and means for compensating for pressure changes of said fluid. v

10. A device for measuring the stress imposed up on a member, comprising a chamber, a piston reciprocal Within said chamber, a

compressible receptacle within said chamber. and adapted to be'compressed by said piston, r r

a rod carried by said piston and extending from the chamber to engage one side of said stressed member, a pair of brackets extending from said chamber on opposite sides thereof, a clamp pivoted to each of said brackets and adapted to engage the other side of said stressed member, means clamps and at the other end to said rod, a fluid 111 said receptacle, and means for measuring the pressure of said fluid.

11. A device for measuring the stress imposed upon a member, comprising a chamber, a piston reciprocal within said chamber, a compressible receptacle within said chamber and adapted to be compressed by said piston, a rod carried by said piston and extending from the chamber to engage one side of said stressed member, a pair of brackets extending from said chamber on opposite sides thereof, a clamp pivoted to each of said brackets and adapted to engage the other side of said stressed member, means for tightening said clamps to deflect said member toward the chamber on opposite sides of the rod, a linkpivoted at the end to each of said clamps and at the other end to said rod, a fluid in said receptacle, means for measuring the pressure of said fluid, and means for compensating for pressure changes of said fluid.

In testimony whereof I have signed my name to this specification.

, OTTO BERGER GOLDMAN.

for tightening said clamps to deflect said member to- 

